Refrigeration appliance with compartments that can be heated and cooled

ABSTRACT

A refrigeration appliance, especially domestic refrigeration appliance, includes a compressor, a condenser, at least a first evaporator, a suction line from the first evaporator to the compressor, at least one heat exchanger switchable between condenser operation and evaporator operation, and a valve arrangement switching the heat exchanger between an evaporator operating state, having a switchable heat exchanger inlet connected to the condenser through a first choke point and a switchable heat exchanger outlet connected to the first evaporator, and a condenser operating state, having the switchable heat exchanger outlet connected to the evaporator through a second choke point. A first supply line for supplying refrigerant in the evaporator operating state and a second supply line, separate therefrom, for supplying refrigerant in the condenser operating state, are associated with the switchable heat exchanger. Only the first supply line is connected with the suction line, forming an external heat exchanger.

The following invention relates to a refrigeration appliance, inparticular a household refrigeration appliance, with at least onecompartment which can be kept at an operating temperature below or abovethe ambient temperature according to a user's choice, in order to coolfood, for example, or keep it warm for imminent consumption.

This variability of the operating temperature is achieved in a knownrefrigeration appliance of the applicant by a condenser, a firstcontrollable choke point, a heat exchanger of the variable compartment,a second controllable choke point and a first evaporator of a cooledcompartment being connected in series in a refrigerant circuit betweenan outlet of a compressor. During cooling operation of the variablecompartment, the pressure drop at the first controllable choke pointhigh, meaning that condensation only takes place in the condenser andthe heat exchanger of the variable compartment also works as anevaporator; during heating operation, the pressure drop substantiallytakes place at the second choke point, meaning that refrigerant alsocondenses in the heat exchanger and in doing so releases heat. In orderto ensure that sufficient heat reaches the heat exchanger, the condenserundergoes forced ventilation, and the power of a fan of the condensermay be reduced compared to cooling operation, in order to control theamount of refrigerant vapor that reaches the heat exchanger, andtherefore to control the heating power of the heat exchanger.

Liquid refrigerant that accrues in the condenser during the heatingoperation should be kept away from the heat exchanger; for this reason,the conventional refrigeration appliance provides a branching pointdesigned as a separator downstream of the condenser, which separates offthe liquid refrigerant in order to use it in a second evaporatorarranged in parallel with the heat exchanger.

A line, which supplies the liquid refrigerant to the second evaporator,together with a suction line, which leads from an outlet of the firstevaporator to an inlet of the compressor, forms an internal heatexchanger in which the liquid refrigerant in thermal contact with thedrawn-in refrigerant vapor cools down. If, as a result of heatingoperation of the variable compartment, the mass flow rate of the liquidrefrigerant is too low, then it may occur that the temperature of theliquid refrigerant lies below its evaporation temperature when reachingthe second evaporator and no evaporation takes place at least in part ofthe second evaporator; in addition, the temperature of the refrigerantvapor when reaching the compressor may still be so low that water vaporcondenses on the suction line, which not only impairs the efficiency ofthe refrigeration, but also may lead to electrical problems andcorrosion.

There is therefore a demand for a refrigeration appliance with at leastone compartment that can be used in heating or cooling operation, inwhich the danger of condensation is reduced, and the degree ofefficiency is improved.

In order to meet this demand, it is provided that on a refrigerationappliance, in particular household refrigeration appliance, with acompressor, a condenser, at least a first evaporator, a suction linerunning from the first evaporator to the compressor, at least one heatexchanger that can be switched between condenser and evaporatoroperation and with a valve arrangement for switching the heat exchangerbetween an evaporator operating state, in which an inlet of theswitchable heat exchanger is connected to the condenser via a firstchoke point and an outlet of the switchable heat exchanger is connectedto the evaporator, and a condenser operating state, in which the outletof the switchable heat exchanger is connected to the evaporator via asecond choke point, the switchable heat exchanger is assigned a firstsupply line for the supply of refrigerant in the evaporator operatingstate and a second supply line, which is separate from the first supplyline, for the supply of refrigerant in the condenser operating state,and that only the first supply line is connected to the suction line toform an internal heat exchanger.

A precooling of the refrigerant reaching the switchable heat exchangerby way of the internal heat exchanger can thus remain restricted to thecase of the evaporator operating state, while in the case of thecondenser operating state a liquefaction of the refrigerant remainsexcluded before reaching the switchable heat exchanger.

In order to be able to vary the pressure drop between the switchableheat exchanger and the first evaporator according to the evaporator andcondenser operating state to a great extent, a controlled expansionvalve is preferably provided as a second choke point between the two.

In order to avoid a loss of heating power that can be used at theswitchable evaporator by way of heat emission via the condenser, it ispossible for the switchable evaporator to be connected in parallel withthe condenser in the condenser operating state. Thus, refrigerant can besupplied to the switchable evaporator immediately after leaving thecompressor, without having the opportunity to emit heat via thecondenser.

A frame heater may be connected upstream of the condenser and theswitchable heat exchanger together, or it may be arranged in series withthe condenser, in parallel with the switchable heat exchanger.

A shut-off valve should be provided at the first supply line in order toenable a blocking of the first supply line in the condenser operatingstate.

Preferably, the refrigeration appliance comprises at least twoswitchable heat exchangers, which can be switched between evaporatoroperating state and condenser operating state independently of oneanother. If these are assigned to compartments of the refrigerationappliance with different sizes in each case, a user can choose betweenvarious volumes of the region that can be used in the condenseroperating state.

Preferably, the volume of one of these compartments amounts to between150% and 250% of the volume of the other.

In order to control the supplying of the switchable evaporator, thevalve arrangement may comprise a directional valve, which in theevaporator operating state is closed and in the condenser operatingstate of at least one of the switchable heat exchangers connects theinlet of the heat exchanger in question to an outlet of the compressor,at least for a time.

Furthermore—and preferably by means of said directional valve—it can bepossible for the valve arrangement to be switched in a clocked mannerbetween a first open position, in which it connects an outlet of thecompressor to the inlet of the first heat exchanger, and a second openposition, in which it connects the outlet of the compressor to the inletof the second heat exchanger. A clocked switching is understood here tomean a periodic switching, wherein the period is short enough to enablecondensation in both switchable heat exchangers at the same time.

A second evaporator may be connected in series upstream of the firstevaporator and connected in parallel with the at least one switchableheat exchanger, in order to be able to cool another compartment at thesame time as the operation of the at least one switchable heat exchangerin the condenser operating state.

If the first evaporator and the second evaporator are connected via athird choke point, the temperature of the second evaporator may be sethigher than that of the first, in order to keep the compartments of thetwo evaporators at different operating temperatures. Typically, in thismanner a normal refrigeration compartment and a freezer compartment canbe implemented; other combinations are of course also possible, such asa normal refrigeration compartment and cold storage compartment or coldstorage compartment and freezer compartment.

A connection line between the first evaporator and the second evaporatormay be connected to the suction pipe to form a section of the internalheat exchanger, in particular this section may connect immediately to anoutlet of the first evaporator, in order to cause a first heating of therefrigerant vapor circulating in the suction line, before it reaches asecond section of the internal heat exchanger, in which the heatexchange with the first supply line takes place.

In order to be able to adapt the temperature difference between thecompartments of the first and the second evaporator to demand, the thirdchoke point also preferably comprises a controlled expansion valve.

Further features and advantages of the invention will emerge from thedescription of exemplary embodiments provided below, with reference tothe attached drawing.

FIG. 1 shows a block diagram of a refrigeration appliance according tothe invention.

In a thermally insulating housing, the refrigeration appliance in FIG. 1comprises a cold cooled compartment 1, typically a freezer compartment,a warm cooled compartment 2, typically a normal refrigerationcompartment, as well as a first and a second flexible, i.e., optionallycoolable and heatable, compartment 3, 4.

A refrigerant line 7, which starts from an outlet 5 of a compressor 6,first reaches a frame heater 9 and a condenser 10 via a branching point8. A fan 26 may be assigned to the condenser 10 in order to control itspower. At a further branching point 11 downstream of the condenser 10,the refrigerant line 7 branches off into three branches 12 a-c. In eachbranch 12 a-c, the following follow one another: a valve 13 a-c, asupply line 14 a-c, which may be embodied as a capillary, a heatexchanger 15 a, b or an evaporator 15 c and a controlled expansion valve16 a-c. The heat exchangers 15 a, b are each in thermal contact with oneof the compartments 3, 4; the evaporator 15 c is in contact with thecompartment 2. There are not necessarily structural differences betweenthe evaporator 15 c and the heat exchangers 15 a, b; both may beidentical or merely different from one another in terms of theirdimensions. Typically, the heat exchangers 15 a, b and the evaporator 15c are embodied as finned heat exchangers of a per se known construction,in which in each case a large number of mutually parallel fins aremerged to form a block, the refrigerant line 7 crosses the fins in ameandering manner and air circulates in the intermediate spaces betweenthe fins, and each finned heat exchanger is assigned a fan 17 a-c, whichcontrols the intensity of the air circulation and therefore the thermalpower exchanged with the compartment 2, 3 or 4 assigned in each case.

Downstream of the expansion valves 16 a-c, the three branches 12 a-cmerge at a junction 18. The junction 18 may lie upstream of anevaporator 19 that cools the compartment 1; preferably, it is located inthe evaporator 19 itself, i.e., the evaporator 19 possesses an inlet foreach branch 12 a-c. In the same way as the fans 17 a-c, the evaporator19 is also assigned a fan 27.

Starting from an outlet of the evaporator 19, a suction line 20 runs toan inlet 21 of the compressor 6. The suction line 20, together with aconnection line 22 of the branch 12 c lying downstream of the evaporator15 c as well as with the supply lines 14 a-c, forms an internal heatexchanger 23, in which the refrigerant vapor circulating in the suctionline 20 is first heated in thermal contact with the connection line 22and subsequently in thermal contact with the supply lines 14 a-c. Forthis purpose, the connection line 22 and the supply lines 14 a-c may befastened to the surface of the suction line 20 or guided in the interiorthereof.

An inlet of a directional valve 24 is connected to the branching point8. The directional valve 24 has an outlet in each case, which isconnected to the inlet of the heat exchanger 15 a or 15 b via a supplyline 25 a or 25 b in each case, and can be switched between the closedposition, a position open toward the heat exchanger 15 a and a positionopen toward the heat exchanger 15 b.

With the construction described above, a large number of operatingstates can be realized:

In a first operating state, the position open toward the heat exchanger15 a and the closed position of the directional valve 24 alternate withone another, the valve 13 a is closed, and the expansion valve 16 a iscontrolled, in order to maintain a high-pressure difference between theheat exchanger 15 a and the evaporator 19. Thus, in each open phase ofthe directional valve 24, warm, dense refrigerant from the compressor 6is applied to the heat exchanger 15 a, and the condensation taking placein the heat exchanger 15 a heats the compartment 3. This means that thefirst operating state is a condenser operating state of the heatexchanger 15 a.

In this context, refrigerant liquefied in the heat exchanger 15 areaches the evaporator 19 via the expansion valve 16 a, evaporates againat the evaporator 19 and thus cools the compartment 1.

In each closed phase of the directional valve 24, dense refrigerantvapor reaches the condenser 10, where it condenses. The liquidrefrigerant obtained in this way is distributed via the valves 13 b, 13c to the supply lines 14 b, 14 c or the heat exchanger 15 b and theevaporator 15 c, meaning that evaporation takes place there and thecompartments 2, 4 are cooled, i.e. the first operating state is anevaporator operating state for the heat exchanger 15 b. Liquidrefrigerant not consumed in the heat exchanger 15 b or evaporator 15 creaches the evaporator 19 via one of the expansion valves 16 b, 16 c,thus contributing to the cooling of the compartment 1.

The level of the heating power (or its operating temperature) releasedin compartment 3 is determined on the one hand by the duty factor of theposition of the valve 13 a in which it is open toward the heat exchanger15 a, and on the other hand by the rotational speed of the fan 17 a; theslower this runs, the slower the condensation, and the less refrigerantvapor can flow into the heat exchanger 15 a, despite the open valve 13a, and the more refrigerant vapor therefore has to take the path via thecondenser 10.

The mass flow rate via the compressor 10 is therefore variable overtime, and with it also the pressure drop at the supply lines 14 b, 14 c.In order to still be able to keep the heat exchanger 15 b and theevaporator 15 c at a desired evaporation pressure, it is recommended touse controlled expansion valves as valves 13 a-c, which are not onlyable to shut off their branch 12 a-c on demand, but also maintain apredefined pressure difference in the open state.

It is also conceivable, however, to tolerate fluctuations in theevaporation pressure in heat exchanger 15 b and evaporator 15 cassociated with the variable mass flow rate and to keep an operatingtemperature of the compartments 2, 4 constant by reducing the rotationalspeed of the fans 17 b, c when the evaporation temperature drops orincreasing it when the evaporation temperature rises.

Thus, in the first operating state, different operating temperaturesbelow the ambient temperature can be maintained in the compartments 1,2, 4, wherein the operating temperature of the compartment 2 may behigher or lower than that of the compartment 4. Both the refrigerantflowing toward the evaporator 15 c and flowing away from it run throughthe internal heat exchanger 23; likewise, the refrigerant on the way tothe heat exchanger 15 b, meaning that all refrigerant, the heat of whichis not needed to heat a compartment, runs through the internal heatexchanger 23.

The same applies for a second operating state, in which the positionopen toward the heat exchanger 15 b and the closed position of thedirectional valve 24 alternate with one another and the valve 13 b isclosed, meaning that the compartment 4 is heated and the compartment 3is cooled, i.e., the second operating state is an evaporator operatingstate for the heat exchanger 15 a and a condenser operating state forthe heat exchanger 15 b.

The compartments 3, 4 have different sizes, thus a user can make theselection between the first and the second operating state on the basisof the space requirement of the item to be kept warm. This means thatthe volume of the compartment 3 may amount to between 150 and 250% ofthe volume of the compartment 4, or vice versa.

In a third operating state, the position open toward the heat exchanger15 a, the position open toward the heat exchanger 15 b and the closedposition of the directional valve 24 alternate with one another. Bothcompartments 2, 3 are heated, i.e., both heat exchangers 15 a, 15 b arein the condenser operating state. As both valves 13 a, 13 b are closed,no heat exchange takes place via the supply lines 14 a, 14 b in theinternal heat exchanger 23; only the flow running via the evaporator 15c is available for the preheating of the drawn-in refrigerant. Via theduty factors of the phases open toward the heat exchanger 15 a or towardthe heat exchanger 15 b, it is possible for the heating power allottedto each compartment 3, 4 to be controlled and for different operatingtemperatures to be set for the two compartments 3, 4, if desired.

In a fourth operating state, the directional valve 24 is permanently inthe closed position. The valves 13 a, 13 b are open, the heat exchangers15 a, 15 b are in the evaporator operating state and cool thecompartments 3, 4. Refrigerant on the way to the heat exchangers 15 a,15 b runs through the supply lines 14 a, 14 b and thus also the internalheat exchanger 23.

Thus, on the one hand, heat losses and condensation of the refrigerantbefore reaching the heat exchanger 15 a or 15 b is avoided when it worksin the condenser operating mode; on the other hand, a higher degree ofefficiency is achieved in the evaporator operating mode.

REFERENCE CHARACTERS

-   1 Compartment-   2 Compartment-   3 Compartment-   4 Compartment-   5 Outlet-   6 Compressor-   7 Refrigerant line-   8 Branching point-   9 Frame heater-   10 Condenser-   11 Branching point-   12 a-c Branch-   13 a-c Valve-   14 a-c Supply line-   15 a-c Heat exchanger/heat exchanger/evaporator-   16 a-c Expansion valve-   17 a-c Fan-   18 Junction-   19 Evaporator-   20 Suction line-   21 Inlet-   22 Connection line-   23 Internal heat exchanger-   24 Directional valve-   25 a-c Supply line-   26 Fan

1-12. (canceled)
 13. A refrigeration appliance or householdrefrigeration appliance, comprising: a compressor; a condenser; at leastone first evaporator; a suction line running from said at least onefirst evaporator to said compressor; at least one heat exchanger havingan inlet and an outlet and being switchable between condenser andevaporator operation; first and second choke points; and a valvearrangement for switching said at least one switchable heat exchangerbetween an evaporator operating state having said inlet of said at leastone switchable heat exchanger connected to said condenser through saidfirst choke point and said outlet of said at least one switchable heatexchanger connected to said at least one first evaporator, and acondenser operating state having said outlet of said at least oneswitchable heat exchanger connected to said at least one evaporatorthrough said second choke point; and a first supply line and a secondsupply line being separate from each other and associated with said atleast one switchable heat exchanger, said first supply line configuredfor supplying refrigerant in said evaporator operating state and saidsecond supply line configured for supplying refrigerant in saidcondenser operating state, and only said first supply line beingconnected to said suction line to form an internal heat exchanger. 14.The refrigeration appliance according to claim 13, wherein said secondchoke point includes a controlled expansion valve.
 15. The refrigerationappliance according to claim 13, wherein said at least one switchableheat exchanger is connected in parallel with said condenser in saidcondenser operating state.
 16. The refrigeration appliance according toclaim 13, wherein said valve arrangement includes a valve configured tobe shut off at said first supply line.
 17. The refrigeration applianceaccording to claim 13, wherein said at least one switchable heatexchanger includes two switchable heat exchangers configured to beswitched between said evaporator operating state and said condenseroperating state independently of one another.
 18. The refrigerationappliance according to claim 17, which further comprises first andsecond compartments, said first compartment having a volume beingbetween 150% and 250% of a volume of said second compartment, and saidtwo switchable heat exchangers being configured to heat or to cool saidfirst and said second compartments.
 19. The refrigeration applianceaccording to claim 17, wherein said compressor has an outlet, and saidvalve arrangement includes a directional valve being closed in saidevaporator operating state and, in said condenser operating state of atleast one of said two switchable heat exchangers, connecting said inletof said at least one heat exchanger to said outlet of said compressor,at least for a time.
 20. The refrigeration appliance according to claim17, wherein said compressor has an outlet, said two switchable heatexchangers are first and second heat exchangers, and said valvearrangement is configured to be switched in a clocked manner between afirst open position connecting said outlet of said compressor to saidinlet of said first heat exchanger, and a second open positionconnecting said outlet of said compressor to said inlet of said secondheat exchanger.
 21. The refrigeration appliance according to claim 13,which further comprises a second evaporator connected in series upstreamof said first evaporator and connected in parallel with said at leastone switchable heat exchanger.
 22. The refrigeration appliance accordingto claim 21, which further comprises a third choke point, said at leastone first evaporator and said second evaporator being connected throughsaid third choke point.
 23. The refrigeration appliance according toclaim 22, wherein said third choke point includes a controlled expansionvalve.
 24. The refrigeration appliance according to claim 21, whichfurther comprises a connection line between said at least one firstevaporator and said second evaporator being connected to said suctionline to form a section of said internal heat exchanger.